Method of purifying oil



Patented Feb; i 18, 19.30 t

luN'iTElo STATES PATENT OFFICE LEE H. CLARK, OF ROSEMONT, PENNSYLVANIA, ASSIGNOR TO THE SHAE'PLE SPE- CIALTY COMPANY, F PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF DELA- WARE METHOD OF PURIFYING OIL Application led July 11, 1925. Serial No. 42,938.

My invention relates to the purification of oil and particularly to a method for the purification or restoration or renovation of oil that contains such impuritiesas products of decomposition or chemical change in the oil or some of its constituents, free fatty acids, water, soaps, sludges usually having an acid reaction, some of which are insoluble and others of which are soluble in the oil at temperatures above norma-l atmospheric temv peratures, or sludge-forming substances and other impurities and that may or maynot contain finely divided carbon which may be wholly or in part colloidal, such impurities having been introduced into the oil during or by reason of the use made of the oil or otherwise.

An object of my invention is to provide a method whereby oil containing some or all of the above mentioned undesirable substances may be brought to a condition wherein itis well adapted to a particular use.

An important example of oil that contains impurities that are removed in the practice of my invention is oil that has been used to immerse transformer coils. Other eX- amples of oils that may be purified in the practice of my invention are oils that have been used to immerse electric switches and circuit breakers and oil that haspbeen used for the lubrication of internal combustion engines. l

In the practice of my invention the resistance of the oil to emulsification may be improved or, if that'propert'y of the oil is satisfactory, it may be preserved or remain unimpaired. In order to improve or maintain 'the resistance of the oil to emulsification it is sometimes desirable in the practice of my invention to take special precautions in'carrying out some of the steps of my process; but if it is desirable to merely remove 'certain impurities from theA oil without regard to the ultimate ability of the oil to resist emulsitication such precautions may be omitted and in some cases some of the steps of my process as completely set forth herein may bewomitted. In any event it is to be understood that with different oils it may be necessary to ascertain by test in accordance with the principles herein set forth what special precautions and what particular steps of my complete invention as herein set forth are to be em loyed to attain the bestmresults.

- ther oils than those specifically mentioned and which contain some or all of the'impurities above mentioned, naturally or by reason of the use to which they have been put, may be purified or restored in accordance with my invention; and although purification of oil in the practice of my invention may neutralize or reduce or otherwise remove the acidity of the oil that effect occurs in the purification thereof and my invention is not to be confused withmere neutralization of sour oils that are produced in the course of acid purification in petroleum rening.

Other and further objects of my invention will appear from the following description.

In purifying, in the practice of my invention, oil that for any reason contains one or more of the above-mentioned impurities, the oil is first treated with finely divided activated carbon and then treated with an aqueous reagent having the properties herein set forth and that is preferably alkaline and may in some instances contain a colloidal substance, after which impurities of the oil and the aqueous phase of the resultin mixture are separated from the oil prefgerably by centrifugal force. If the oil so treated possesses the desired properties no further treatment ,is necessary but in some cases further purification such as the removal of traces of moisture from the oil may be effected yby passing the oil through a centrifugal clarifier; and if it be desired to remove such moisture and additional impurities that impair the resistance to emulsiication of the oil that is separated from the aqueous reagent, such results may be effected by treating the oil with an adsorptive medium that is subsequently removed from the oil. As a variation of the foregoing procedure the acti' i rectly added to and agitated with the oil, the

carbon preferably being in a finely divided stateand preferably not exceeding 17d-by weight of the oil to which it is added. '-As above stated the viscosity of the oil maybe reduced during this operation.

The aqueous reagent, in accordance with my invention, must have the property of being more readily dispersed throughoutl the oil than substantially pure water and it must have the property of facilitating or causing impurities of the oil to pass from the oil to the interface between the aqueous reagent and the oil or through that interface into the aqueous reagent; and the aqueous reagent preferably has such consistency or composition or Y 'such properties that water soluble products of any reaction between the reagent and the oil or its impurities will dissolve in it. The aqueous reagent may consist of an aqueous solution of caustic soda, soda ash, tri-sodium phosphate, or other alkaline substances that produce the desired effect while in solution. In the practice of my invention advantage may be gained by the 'useof an aqueous reagent of which at least some part of the substance present is in colloidal suspension or solution. An effective solution of such char\ acter may be produced by the use of sodium silicate, particularly sodium silicate in which silica predominates by weight, for example in which there are 3.25 arts by weight o f SiO2 to each part of Nazg, or sodium aluminate or sodium tungstateor any reagent that gives sufficient alkaline concentration and in addition gives naturally, or can be made to give by combination with other agents, the required colloidal condition. This condition is attainable by introducing substances varyf .ing from finely divided silicato aluminum hydroxide.

In the practice of my invention good results are attainable by the use of an aqueous reagent having an alkalinity, available underthe existing conditions though not in every case initially free, equivalent to that of a solution containing 1% to 1% by weight of caustic soda, a solution having an alkalinity equivalent'to such a M270` solution of lcaustic Y soda havingbeen found generally applicable and convenient for commercial work. `In any event the degree of alkalinity of the kreagent `must be such as torender the reagent capable of being easily dispersed in oil and capable of causing removal of impurities therefrom, excessive alkalinity being avoided in Vorder that soaps present in the oil or formed with the fattyacid or acid reacting substances thereof may not be prevented 'from dissolv-y ing in the aqueous'phase of the resulting mixture. If, in the practice of my invention, the activated carbon is not added directly to the oil it will be mixed with^ the aqueous reagent and so introduced to the oil.

In the practice of my invention the aqueous reagent is mixed with the oil preferably by agitation suiiiciently violent and prolonged .to carry small particles or globules of the reagent to close proximity but not necessarily into contact with every part of theoil that is to be purified. The mixture is advantageously maintained in a heated state, for example 150o F. to 200 F. during the agitation thereof, the temperature being dependent upon the viscosity of the oil. A

The aqueous phase and impurities including the activated carbon are then separated found that no rocess has been suggested by others for puri ying oil containing the abovementioned impurities whereby centrifugal machines may be em loyed and that no puri-` fying agents heretofbre suggestedy by others make it possible to effect the separation in a 'Y centrifugal machine.

The 'aqueous reagent should be suiicient Ain quantity and strength to satisfy the affinities of the impurities in the oil and still vprovide a sufficient excess of active reagent to insure that the reagent will be dispersed throughout the oil andcause the impurities to be removed therefrom as by passing into or dissolving in the aqueous phase of theresulting mixture. The relative quantity of aqueous reagent added to the oil may` vary in the treatment of different oils and oils. containing dierent impurities. If the oil that is discharged from the centrifugal separator is found by examination or test to have been sufliciently purified so that either with or without further treatment in accord-l ance with my invention as herein described,

it is suitable or may be made suitable for reuse, the alkaline concentration of the reagent and the quantity mixed with the oil is correct. But, if the oil does not appear to be f suiiiciently purified that is an indication that the conditions of the aqueous phase were incorrect for the particular oil treated. Thus, if the oil discharged from the centrifugal separator appearsto be insuficiently purified and the aqueous discharge from the separator is turbid but light in shade, the degree of alkalinity of the reagent was insufficient to effect a substantial removal of the impurities. On the other hand, if the aqueous discharge contains a high concentration ofremoved impurities and the oilappears to have been insufficiently. purified, the mixture producedby the agitation contained an linsufficient proportion .of the aqueous phase". In the 'practice of myfinvention I have found that satisfactory results are atthe reaction between the reagent and the oil or impurities thereof will form a sludge that prevents impurities from passing from oil to the aqueous phase, that cannot be completely separated from the oil either by gravity or centrifugal force, and that carries into the oil impurities that should be removed therefrom. By the use of a reagent having the properties above set forth no sludge layer is formed between the oil and the aqueous phase. It is because all impurities of products thereof that are Water soluble are in solution that it is possible to separate the aqueous phase and impurities and sediment from the oil by centrifugal force. Thus, the purification of oil in accordance with my invention makes it possible for the first time to remove impurities of the character above-mentioned by centrifugal force but removal in that manner is not essential to my invention.

impure oil that has been treated with activated carbon and also treated with an aqueous reagent as above set forth and then passed through a centrifugal separator may be sufhciently purified to meet the requirements of the purpose for which the oil is t0 be used, but oil that has previously been so treated may be further purified by being passed through a centrifugal clarifier, such clarification .removing residual water and' other impurities. If the oil discharged from the centrifugal separator in the practice of my invention as above set forth requires further treatment, particularly if the resistance to emulsiiication of such oil is to be i improved, adsorptive material is now added to the oil and agitated therewith and the resulting mixture is then advanta eouslypassed through a centrifugal clari er. Y I

have found that the addition to oil discharged from the centrifugal separatorv of only small amounts, of the order 1/4% to 1%, of adsorptive material will'eect purification and improvement of the resistance such condition that such small amounts'of adsorptive material will further purify it and effect that purification or alteration of the oil whereby its resistance to emulsiflca-T tion is made satisfactory.. If the'resistance of the impure oil to emulsication 1s not particularly poor, treatment ofthe oil as above described with a reagent containing no colloidal substance will not improve that resistance but after such treatment such small amounts of adsorptive material will make that resistance, even thoughl originally poor', satisfactory. If the resistance of the impure oil to emulsiiication is originally very poor that resistance is im roved when a reagent containing a colloida component is used and is made entirely satisfactory by further treatment with such small percentage of adsorptive material.

My process above described is particularly effective in the purification'of transformer oil, and oils containing sludge, especially sludge that is soluble at increased temperature.

In the treatment of certain oils the results may be improved by delaying the introduction into the clarifier of oil discharged from the centrifugal separator. While the centrifugal separator may be so handled in the operation of separating vthe aqueous phase impurities and activated carbon from the oil, that the oil discharged from theseparator is sufficiently free of moisture, operation of the separator to secure such a result' may be less eiicient than a less careful handling of the separator' followed by centrifugal clarification. i

While l have referred only to activated carbon I, d0 not intend to be limited-to anypar` ticular form of carbon but intend that the use of any carbon that is adsorptive and falls within the class of decolorizing or deodorizing carbons is within the spirit of my invention.' While I have found that the use of such carbon in the manner and for the purpose herein set forth produces highly satisfactory results I do not venture any theory in explanation of the manner in which those results are produced.

Purificationof oils contaminate-d as above described cannot be effected by methods heretofore known such as previously known centrifugal processes or filtering devices, except that purification of such oils may be effected as set forth in my co-pending Patent No.

1,553,141 issued September 8th, 1925. And, it will be apparent from the foregoing disclosure that in accordance with m invention oils contaminated as above descri ed may be put into conditionfor theparticularI use for which they are desired 'and the resistance of the oil to lemulsifcation may be improved by the selection of the aqueous reagent used or by treatment with an adsorptive medium after treatment with a suitable aqueous reagent or by both of these treatments, it being possible that the useagf activated carbon also improves the resistance of the oil to emulsification. Unless sludge soluble above 100 F.

and substances forming soluble sludge are removed, the oilwill become cloudy after treatment, and substances ordinarily used for the purification of oil form with such sludge, or sludge-forming substances, compounds which are highly soluble in the oil and which leave the oil contaminated. However, purifying treatment in accordance with my invention so completely purifies oil containing such substances that a high degree of p urity is indicated by even such tests as the tests for resistance to emulsification.

In the practice of my invention vthe amount ofactivated carbon added to the oil will ordinarily be less than 1% of the oil byweight but it may be found in practice that, additional activated carbon should be used. In the practice of my invention I have found that a suitable aqueous reagent may consist of a solution containing 2% by Weight of sodium silicate of the composition above set forth; and that satisfactory results are obtained by mixing such aqueous reagent Withfthe oil in the proportions above set forth. I have also found that caustic soda solution containing 1/% of caustic soda will give satisfactory results. With such anaqueous reagent water soluble products of any reaction between the reagent and' the oil or any of its impurities, including products of saponification, will `be soluble in the aqueous phase and ifa niixture of impure oil and such reagent is settled by gravity no layer of sludge will be 'formed between the oil and the aqueous phase and the entry of finely divided carbon into the aqueous phase is not interfered with. 'It is because these conditions exist in my process that the aqueous phase and sediment may be separated by centrifugal force. If the oil to' be purified contains relatively high percentages of acid impurities it is better to increase the proportion of reagent to the oil than to increase the alkaline concentration of. the aqueous reagent.

For the purpose of rendering more quickly apparent the general features of my invention and one mode of operation thereof, there is shown in the annexed drawings one application of my invention to the purification 'of oil and some of the many possible modifications of that applieationof Amy invention. Thus, in the drawings, t

Fig. 1 shows schematically one group of steps that may. be followed inthe practice of lmy invention; and

Fig. 2 shows schematically a modification of some of the first stepsindicated in Fig. 1. Figs. 1 and 2 may be considered as flow sheets in certain applications of my invention, the branches A-and B in Fig. 1 indicating alternative treatments of oil recovered in *f the separating step, either of which may be applied to such oil after the steps shown in Fig. 2 are carried out.

It is to be understood, however, that my invention is not limited to the general o peration or to the modifications thereofshown in the drawings inasmuch as the invention may.

be embodied in other general operations and may include modifications that are not shown 'in the drawings.. It is also to be understood and modifications as fall within the hereunto appended claims. v l

lVhat I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of purifying mineral oil that contains decomposition products, free fatty acid and sludge or sludge forming substances which lcomprises contacting such oil with activated carbon and dispersing in the oil an aqueous alkaline reagent containing a uni-valent alkali, and separating from the oil together the activated carbon, impurities and the aqueous phase of the resulting mixture.

2. The method of purifying mineral oil that contains decomposition products', free fatty acid and sludge or sludge forming substances which comprises mixing finely divided activated carbon with such oil and dispersing an aqueous alkaline reagent in said oil containingsaid carbon and thereby producing an' emulsion, and separating from the oil -thc activated carbon, impurities and the aqueous phase of the resulting mixture.

3. The method of purifying mineral oil which comprises contacting the oil with activated carbon and an aqueous alkaline reagent, separating from the oil the activated carbon, impurities and the aqueous phase of the resulting mixture, and then treating the oil with adsorptive material and thereby improving its resistance to emulsification'.

4. The method of purifying mineral -oil which comlfrises contacting the oil with not more than 1% by Weight of finely divided activated carbon, dispersing in the oil containing such carbon an aqueous alkaline neagent, and centri-fugally separating from the oil together the activated carbon, impilrities and the aqueous phase of the resulting mixture.

5. The method of purifying mineral oil which comprises contacting the oil with not more than 1% by weight of finely divided activated carbon, mixing the o-il with an aqueous alkaline reagent, centrifugally separating from the oil the activated carbon, im; purities and the aqueous phase of the resulting mixture, and then treating the recoveredA fatty acids and sludge or sludg-forming substances which comprises contacting Vsuch oil simultaneously with 4activated carbon and an aqueous alkalme reagent contaming a .um-

valent alkali and separating from the oil together the activated' carbon, impurities and the aqueous phase of the resulting mixture.

7. The method of purifying impure mineral oil which comprises contacting the oil With activated carbon and dispersing throughout the oil an aqueous alkaline reagent sufficiently dilute that Water soluble impurities and Water soluble products of any reaction produced by the reagent Will be in solution in the aqueous phase of the resulting mixture, and separating from the oil the activated carbon, impurities and the aqueous phase of the resulting mixture.

8. The method of purifyingimpure mineral oil which comprises contacting the oil With finely divided activated carbon, dispersing thrughout the oil an aqueous alkaline reagent suiiciently dilute that Water soluble impurities and products of saponiication Will be in solution in the aqueous phase ofthe resulting mixture, and separating from the oil the activated carbon, impurities and the aqueous phase.

9. The method of purifying impure mineral oil Which comprises contacting the oil with finely divided activated carbon, dispersing throughout the oil an aqueous alkaline reagent sufficiently dilute that Water soluble impurities and Water soluble pro-ducts of any reaction produced by the reagent will be -in solution in the aqueous phase of the resulting mixture, separating from the oil activated carbon, impurities and the aqueous phase, and treating the recovered oil With adsorptive material and thereby increasingthe resistance of the oil to emulsification with Water.

10. The method of purifying impure mineral oil which comprises contacting the oil with finely divided activated carbon, dispersing throughout the oil aqueous alkaline reagent capable of being easily dispersed Within the oil and having the property of facilitating the passage of carbonaceous impurities from the oil into the aqueous phase of the resulting mixture and containing in suspension colloidal substance ca able of causing carbon particles to lie Wlthin the aqueous phase, and separating from the oil the aqueous phase and impurities.

11. The method of purifying mineral oil 'which comprises contacting the oil with finely divided activated, carbon, dispersing throughout the oil an aqueous alkaline reagent containing a substance in colloidal form, and separating from the oil the activated carbon, impurities and the aqueous phase of the resulting mixture.

12. The method 4of purifying impure mineral oil which comprises contacting the oil.

with finely divided activated carbon, dispersing throughout the oil an aqueous alkallne reagent containing a colloidal substance 1n suspension and suiciently dilute that Water soluble impurities and water soluble products ofiany reaction produced by the reagent will be in solutionin the aqueous phase of the rethat contains decomposition products, freel y 'fatty acid and sludge or sludge forming substances Which comprises contacting the oil with activated carbon and mixing the oil with an aqueous alkaline reagent, separating from the oil together the activated carbon, impurities and the aqueous phase of the resulting mixture, and then treating the 'oil with adsorptive material.

14. The method of purifying mineral oil that contains decomposition products, free fatty acid and sludge or sludge forming substances Which comprises contacting the oil With activated carbon and mixing the oil With an aqueous alkaline reagent, separating from the oil the activated carbon, Yimpurities and the aqueous phase of the resulting mixture, and then treating the oil With not more than one percent by Weight of adsorptive materia 15. The method of purifying mineral oil containing decomposition products, vfree fatty acid and sludge or sludge-forming substances, Which comprises simultaneously contacting the oil With activated carbon and dispersing in the oil an aqueous solution of sodium silicate and thereby producing an emulsion containing an aqueous phase, and separating from the oil together the activated carbon, impurities and the aqueous phase of the resulting mixture. Y 4K16. The method of purifying mineral oil which comprises simultaneously contacting the oil Withnot substantially more than one percent by Weight of activated carbon and with' aqueous alkaline reagent in the proportion of eight to ten parts of oil to one part of aqueous alkaline reagent, and separating and the aqueous phase of the resulting mix"-Y` ture.

18. In the purification of mineral oil, the

process comprising introducing not substantially more than one percent by Weight of activated carbon into oil contaminated by use for submersion of electrical apparatus and dispersing in the oil an aqueous alkaline solution and thereby producing a mixture' having an aqueous phase, and separating fromthe oil together the activated carbon, 1mpur1t1es and the aqueous phase of the resulting mixture,

19. The method of purifying mineral oil that contains decomposition products includ-1 ing soluble sludge, which comprises contact# ing such oil with nely divided activated carbon, dispersin'g in the oil containing such carbon an aqueous alkaline reagent containing a uni-valent alkali, and centrifugally separating from the oil immscible solids and the aqueous phase of the resulting mixture.

In testimony whereof', I have signed my name to this specification.

LEE H. CLARK. 

